THIS DOCUMENT IS FOR MAINTENANCE
PURPOSES ONLY AND IS NOT
RECOMMENDED FOR NEW DESIGNS
AUGUST 1994
DS3007-2.1
ZN428E8/ZN428J8/ZN428D
8-BIT LATCHED INPUT D-A CONVERTER
The ZN428 is a monolithic 8-bit D-A converter with input
latches to facilitate updating from a data bus. The latch is
transparent when enable is LOW and the data is held when
enable is taken HIGH. The ZN428 also contains a 2.5V
reference the use of which is pin optional to retain flexibility.
An external fixed or varying reference may therefore be
substituted.
BIT 7
BIT 8
NC
ENABLE
ANALOG OUTPUT
V
REF
IN
V
REF
OUT
ANALOG GROUND
1
2
3
4
5
6
7
8
16
15
14
ZN428J8
13
ZN428E8
12
11
10
9
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
+V
CC
(+5V)
DIGITAL GROUND
FEATURES
s
Contains DAC with Data Latch and On-Chip
Reference
s
Guaranteed Monotonic over the Full Operating
Temperature Range
s
Single +5V Supply
s
Microprocessor Compatible
s
TTL and 5V CMOS Compatible
s
800ns Settling Time
s
Complementary to ZN427 A to D Series
s
Commercial or Military Temperature Range
ORDERING INFORMATION
Device Type
ZN428D
ZN428E8
ZN428J8
Operating temperature
0
°
C to +70
°
C
0
°
C to +70
°
C
-55
°
C to +125
°
C
Package
MP16W
DP16
DC16
DC16
DP16
BIT 7
BIT 8
NC
ENABLE
ANALOG OUTPUT
V
REF
IN
V
REF
OUT
ANALOG GROUND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
+V
CC
(+5V)
DIGITAL GROUND
ZN428D
MP16 WIDE BODY
Fig.1 Pin connections (not to scale) - top view
ZN428
ABSOLUTE MAXIMUM RATINGS
Supply voltage V
CC
Max.voltage, logic and V
REF
inputs
Operating temperature range
Storage temperature range
Analog ground to digital ground
+7.0V
+V
CC
0
°
C to +70
°
C (ZN428E8, ZN428D)
-55
°
C to +125
°
C (ZN428J8)
-55
°
C to +125
°
C
±
200mV
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V, T
amb
= 25
°
C unless otherwise specified)
Parameter
Min.
Typ.
Max.
Units
Conditions
Internal Voltage Reference
Output voltage
Slope resistance
V
REF OUT
T.C.
Reference current
D-A Converter
Linearity error
Differential non-linearity
Linearity error T.C.
Differential non-linearity T.C.
Offset voltage
Offset voltage T.C.
Full-scale output
Full-scale output T.C.
Analog output resistance
External reference voltage
Settling time to 0.5 LSB
2.475
-
-
4
-
-
-
-
-
-
2.545
-
-
0
-
-
2.550
0.5
50
-
-
±
0.5
±
3
±
6
2
±
6
2.550
2
4
-
800
1.25
2.625
2
-
15
±
0.5
-
-
-
5
-
2.555
-
-
3.0
-
-
V
Ω
ppm/
°
C
mA
LSB
LSB
ppm/
°
C
ppm/
°
C
mV
µ
V/
°
C
123
123
R
REF
= 390
Ω
C
REF
= 1
µ
F
Note 1
2.0V
≤
V
REF IN
≤
3.0V
All bits off
ppm/
°
C
k
Ω
V
ns
µ
s
External reference
V
REF IN
= 2.560V,
all bits ON
1 LSB major transition
(Note 2)
All bits ON to OFF or
OFF to ON (Note 2)
Operating temperature range:
ZN428D and ZN428 E8
ZN428J8
Supply voltage (V
CC
)
Supply current
Power consumption
Note 1: See REFERENCE
Note 2: R
L
= 10M
Ω
, C
L
= 10pF
Note 3: All inputs HIGH (V
IH
= 3.5V)
0
-55
4.5
-
-
-
-
5.0
20
100
70
125
5.5
30
-
°
C
°
C
V
mA
mW
Note 3
ZN428
ELECTRICAL CHARACTERISTICS
(cont.)
Parameter
Logic
(over specified operating
temperature range)
High level input voltage
Low level input voltage
High level input current
Low level input current
Input clamp diode voltage
Enable pulse width
Data set-up time
Data hold time
Note 4: Set up time before ENABLE goes high
Note 5: Hold time after ENABLE goes high
2.0
-
-
-
-
-
100
150
10
-
-
-
-
-
-1.5
-
-
-
-
0.8
60
20
-5
-
-
-
-
V
V
µ
A
µ
A
µ
A
V
ns
ns
ns
Note 4
Note 5
V
IN
= 5.5V, V
CC
= Max.
V
IN
= 2.4V, V
CC
= Max.
V
IN
= 0.4V, V
CC
= Max.
I
IN
= -8mA
Min.
Typ.
Max.
Units
Conditions
D-A CONVERTER
The converter is of the voltage switching type and uses
an R-2R ladder network as shown in Fig.3. Each 2R element
is connected to 0V or V
REF IN
by transistor voltage switches
specially designed for low offset voltage (<1mV). A binary
weighted voltage is produced at the output of the R-2R
ladder.
Fig.3 The R-2R ladder network
Analog output =
n
(V
REF IN
- V
OS
) + V
OS
256
where n is the digital input to the D-A from the data latch.
V
OS
is a small offset voltage produced by the D-A switch
currents flowing through the package lead resistance. The
value of V
OS
is typically 1mV. This offset will normally be
removed by the setting up procedure (see Operating Notes)
and because the offset temperature coefficient is low
(
±
6
µ
V/
°
C)the effect on accuracy is negligible.
ZN428
Fig.4 Analog output equivalent circuit
Fig.4 shows equivalent circuit of the output (ignoring
V
OS
). The output resistance R has a temperature coefficient
of +0.2% per
°
C.
The gain drift due to this is
0.2R
% per
°
C.
R+R
L
R
L
should be chosen as large as possible to make the
gain drift small. As an example if R
L
= 400k
Ω
then the gain
drift due to the T.C. of R for a 100
°
C change in ambient
temperature will be less than 0.2%. Alternatively the ZN428
can be buffered by an amplifier (see Operating Notes).
REFERENCE
(a) Internal Reference
The internal reference is an active bandgap circuit which
is equivalent to a 2.5V Zener diode with very low slope
impedance (Fig.5). A resistor (R
REF
), should be connected
between +V
CC
(pin 10) and pin 7. The recommended value
of 390
Ω
will supply a nominal reference current of (5.0-
2.5)/0.39 = 6.4mA. A stabilising/decoupling capacitor C
REF
=
1
µ
F is required between pins 7 and 8 for internal reference
option, V
REF OUT
(pin 7) being connected to V
REF IN
(pin 6).
Fig.5 Internal voltage reference
京公网安备 11010802033920号
EEWORLD
